Invisible Stimuli,Implicit Thresholds: Why Invisibility Judgments Cannot be Interpreted in Isolation

Some studies of unconscious cognition rely on judgments of participants statingthat they have “not seen” the critical stimulus (e.g., in a masked-primingexperiment). Trials in which participants gave invisibility judgments are thentreated as those where the critical stimulus was “subliminal” or “unconscious,”as opposed to trials with higher visibility ratings. Sometimes, only thesetrials are further analyzed, for instance, for unconscious priming effects. HereI argue that this practice requires implicit assumptions about subjectivemeasures of awareness incompatible with basic models of categorization underuncertainty (e.g., modern signal-detection and threshold theories). Mostimportantly, it ignores the potential effects of response bias. Instead oftaking invisibility judgments literally, they would better be employed inparametric experiments where stimulus visibility is manipulated systematically,not accidentally. This would allow studying qualitative and double dissociationsbetween measures of awareness and of stimulus processing per se.